Long-Sought Uranium(VI) Nitride Complex Isolated

The chemistry of uranium and other actinide compounds has use in catalysis, nuclear fuels, and nuclear waste treatment and can help explain the role of f orbitals in bonding and reactivity. Uranium nitride complexes are of particular interest for nuclear fuels because they have greater thermal conductivity than oxide complexes. Following up on the isolation of the first uranium(V) complex with a terminal nitride ligand last year, a group in England led by the University of Nottingham’s Stephen T. Liddle has now isolated the first uranium(VI) terminal nitride complex (Nat. Chem., DOI: 10.1038/nchem.1642). Liddle and colleagues prepared it by first making the uranium(V) nitride complex, which incorporates a tetradentate tris(2-amidoethyl)amine-based ligand. They then oxidized the uranium(V) complex to uranium(VI) using I₂. They found that the uranium(VI) nitride complex is sensitive to photochemical decomposition, which likely explains why previous attempts to isolate such compounds failed. Computational analysis of the uranium nitride compounds shows that the U≡N bond is more covalent than the researchers expected and is similar to those of group 6 transition-metal nitride compounds, Liddle says.